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Radiologic Exposures > Final Review:Contrast > Flashcards

Final Review:Contrast Flashcards

1
Q

Difference between adjacent gray shades/image receptor exposures

A

Image Contrast

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2
Q

Two photographic factors allow detail to be seen:

A

-IR exposure
-Contrast

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3
Q

Dynamic Range

A

gray scale, Window Width
Range of brightness displayed on monitor

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4
Q

Receptor Exposure

A

How much is reaching the IR

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5
Q

Bit Depth

A

Shades of gray

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6
Q

Determines the dynamic range of image in digital systems (controls contrast)

A

Look up table

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7
Q

Short scale
-few shades of gray between lightest and darkest
-short/narrow dynamic range

A

High Contrast

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8
Q

Long scale
-more shades of gray between lightest and darkest
-large/ wide dynamic range

A

Low Contrast

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9
Q

Why is high contrast not necessarily a good thing in medial imaging

A

More shades of gray can reveal more information

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10
Q

Manipulating contrast

A

Compression or expansion of range of visible densities
-adjustment to kvp
-Window width left and right

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11
Q

Subject contrast is dependent on:

A

-kvp
-amount of irradiated material
-Type of irradiated material

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12
Q

What causes wider range of photon energy?

A

-greater penetrability
-greater range of exposures
-greater amount of scatter
-longer scale of contrast (film)

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13
Q

Higher kvp produces how much range of exposure

A

narrower range of exposures picked up by IR (yields a narrower histogram)

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14
Q

Excessive kvp’s reduce differential absorption and therefore limits the range of exposure values picked up by the IR. What can this lead to

A

Can lead to histogram errors

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15
Q

If the kvp does not match the subject contrast, what is being impacted?

A

Differential absorption

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16
Q

Increase in thickness and field size does what to the scatter and scale of contrast?

A

-increases scatter
-longer scale of contrast (film)

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17
Q

The amount of irradiated material is dependent on:

A

Thickness or part and field size

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18
Q

Type of irradiated material is influenced by:

A

Atomic number and tissue density

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19
Q

What does high atomic number and tissue density do to attenuation and photoelectric interactions

A

-greater attenuation
-more photoelectric interactions

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20
Q

Large differences in atomic number and tissue density of adjacent tissues

A

High Contrast

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21
Q

What is the primary controlling factor for the the patient

A

kvp

22
Q

Why can’t the subject contrast be manipulated

A

Because it is the patient (tissue)

23
Q

For a nongrid, what number should you not exceed?

A

80 kvp

24
Q

Cannot be assessed by visualization

A

kvp

25
Q

what scatter ration requires use of grids

A

greater than 50%

26
Q

does focal spot effect contrast?

A

No affect of contrast

27
Q

how does more matter affect contrast

A

decreases contrast

28
Q

how does collimation affect contrast

A

Increased collimation increases contrast and decreases scatter

29
Q

does the anode heel affect have any affect on contrast

A

no effect on contrast but effects receptor exposure

30
Q

does SID affect contrast

A

SID only affects receptor exposure, not contrast

31
Q

Air Gap Technique

A

6 to 8 inch gap to decrease scatter on IR. Increases contrast because scatter is not reaching IR.

32
Q

Increased filtration decreases quantity but increases quality

A

Filtering out low energy photons

33
Q

Increased filtration, decreased ESE

A

More to IR, less absorption. More transmission, filtering out low energy photons

34
Q

Increased Filtration does what to beam energy and contrast?

A

Increased average beam energy and decreased contrast (film)

35
Q

How is grid ratio and contrast related?

A

Directly. Increased grid ration increases contrast (more black and white because more clean up removing scatter)

36
Q

Differences in density between two areas on an image

A

contrast

37
Q

Long scale contrast

A

many shades of gray visible

38
Q

short scale contrast

A

mostly blanks and whites present

39
Q

Large differences in density

A

high contrast

40
Q

small density differences

A

low contrast

41
Q

Range of exposures that will produce radiograph in the diagnostic range of densities

A

Exposure Latitude

42
Q

Latitude inverse relationship to contrast:

A

Wide latitude = low contrast
Narrow latitude = high contrast

43
Q

Latitude relationships to gray scale:

A

Wide latitude= long gray scale contrast
Narrow latitude= short gray scale contrast

44
Q

Example of long scale contrast:

A

Abdominal xrays or chest xrays

45
Q

Example of short scale contrast:

A

Hand xrays (bony anatomy)

46
Q

Look up table

A

Picture perfect image, manipulates values of gray levels, controlling contrast

47
Q

is brightness in film or digital

A

digital (monitor)

48
Q

Is density film or digital

A

Film

49
Q

What are some of your subject contrast?

A

kvp
amount of irradiated material
type or irradiated materal

50
Q

Differential absoprtion

A

Will it either transmit or absorb

51
Q

Window width
Window leveling
Annotation
Any manipulation to an image

A

Post processing

52
Q

Bit depth
Look up table
Histogram

A

Pre processing

Radiologic Exposures (11 decks)

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